1. Field of The Invention
In pipe systems, e.g. located below the ground plane, formation of cracks or fractures can occur, caused by variations in temperature, movement in surrounding material, pressure changes and similar causes. When such pipe systems are located in a position difficult to access, repairs cause obvious problems, e.g. due to the fact that the pipe system must be freed from surrounding material in order to facilitate repair or exchange of a damaged part.
2. Description Of The Prior Art
In U.S. Pat. No. 2,977,994, a method is disclosed for repair of a pipe system, in which a flexible tubular hose is inserted into a pipe system in a deformed or compressed cross-sectional condition, retained in said deformed condition by means of releasable members, whereby the hose after insertion into the pipe system can be expanded to take up a mainly circular cross-sectional position, extending in contact with the internal wall surface of the pipe system.
The above discussed method of repairs makes it thus possible to arrange a flexible hose as an internal restricting surface in an existing pipe system, but for many applications it is desirable to provide an internal metallic surface, in order to obtain resistance against existing variations in temperature and pressure, as well as certain types of liquid and gaseous mediums, which are transported in the pipe system. For certain applications, repair can be performed with a pipe having a smaller diameter than the pipe to be repaired, and by insertion of same into an embraced relationship to the damaged pipe, but to facilitate this operation, the inserted pipe must have a considerably smaller cross-sectional area than the outer pipe, in order to facilitate insertion, and seals must be arranged at the outer end portions of the inserted pipe in contact with the surrounding outer pipe. Said reduction in area is an obvious disadvantage, and it is also extremely difficult to provide seals between the end portions of the inserted pipe and the surrounding pipe, whereby the method only occasionally can be used.